The present invention relates to a microsolenoid coil which can be formed into a lateral or longitudinal spiral coil having a section of a circle that is nearly a complete circle by controlling exposure drawing on a photosensitive material, and a method of manufacturing the same.
An inductance such as a solenoid coil or the like has often been used thus far in electric circuits other than microcircuits, such as in a semiconductor integrated circuit and the like. In microcircuits such as a semiconductor integrated circuit and the like, a transistor, a resistor, a condenser and the like are used. However, an inductance such as a solenoid coil involves many technical problems in that it is, in comparison with other elements, complex and difficult to manufacture.
A schematic view of a projection exposure device used in a lithographic step of baking a pattern which is one step of manufacturing a semiconductor is shown in FIG. 26. The view shown therein indicates that a photosensitive material 10 is of a positive type, and after development the photosensitive material 10 to which a light is not applied remains, and the photosensitive material 10 to which a light is applied is removed. A light 4 emitted from a light source transfers a pattern onto a mask M onto the photosensitive material 10 on a substrate 1 in a lightness and darkness form. For example, when a pattern made of an annular light-shielding film 8 is exposed through projection and developed on the substrate 1, the photosensitive material 10 is doughnut-shaped, and never spiral. The mask M used conventionally is made only of a glass 7, and transmits a light by approximately 100% in a region free of the light-shielding film 8, while it has a light transmittance of 0 and does not transmit a light in a region having the light-shielding film 8.
In order to solve the problems of this kind of the inductor element, a manufacturing technique is proposed in, for example, Japanese Patent Laid-Open Nos. 189,339/1998 and 313,093/1998. With respect to a method of forming a lateral coil, Japanese Patent Laid-Open No. 189,339/1998 discloses a technique in which an isotropic etching method or a method of a combination of anisotropic etching and isotropic etching is used as a method of forming a semicircular groove, and whereby polysilicon or amorphous silicon previously embedded in a groove portion is then stacked and expanded by oxidation for forming a cylindrical shape of a coil section. Further, Japanese Patent Laid-Open No. 313,093/1998 discloses a technique in which flat spiral inductors are vertically stacked via an insulation layer, and whereby, at this time, the upper and lower inductors are selectively connected spirally via through-holes formed in the insulation layer to form a two-layer spiral coil.
Incidentally, a filter circuit is inherently formed by a combination of a resistor, a condenser and a coil. A filter circuit formed on an existing semiconductor integrated circuit is however constructed by using a resistor, a condenser and a transistor. Since a coil is not used, a large number of parts, resistors, condensers and transistors are required to realize a filter circuit having desired characteristics, and chip size is thereby increased. In addition, transistors tend to be influenced by the temperature of the usage environment. Thus, the larger the number of transistors used, the more unstable the characteristics of the overall circuit tend to be.
Moreover, as the scale of the integrated circuit becomes larger, a wiring width of an electric wiring in the integrated circuit is more decreased, and the wiring route becomes longer, with the result that wiring resistance and the capacitance of wirings are increased. Consequently, there arise problems such that the speed of charge passing through wiring is controlled, and the rate of delay of a current is increased.
Meanwhile, in a technique disclosed in Japanese Patent Laid-Open No. 189,339/1998, as a method of forming an inductor element on a substrate, a method of forming a cylindrical portion of a lateral coil includes an isotropic etching method, or a method of a combination of anisotropic etching and isotropic etching and a method in which polysilicon or amorphous silicon is stacked and expanded by oxidation. Therefore, with this method, it is difficult to form a cylindrical section in the shape of a complete circle with high precision. For this reason, a change in the magnetic field cannot be uniformly maintained.
Further, the technique disclosed in Japanese Patent Laid-Open No. 313,093/1998 is problematic, in that the spiral coil in which the upper and lower coils are spirally stacked via the through holes leaks a magnetic flux outside the coil in comparison with a solenoid coil, and a change in the magnetic field thus cannot be rendered uniform.
The invention aims to provide a microsolenoid coil in which an inductance value can easily be increased by controlling an occupied area of a coil in a substrate, and whereby a change in the magnetic field can uniformly be maintained by retaining the magnetic flux within the coil.
The invention completes a lateral spiral coil by connecting a metal wiring of a lower half formed first with a metal wiring of an upper half formed finally.
Further, the invention completes a coil of a longitudinal spiral structure with multiple winding by stacking spiral metal windings thus formed.
According to the invention, an inductance value can easily be increased by controlling an occupied area of a coil in a substrate, and a change in a magnetic field can uniformly be maintained by retaining the magnetic flux within the coil.
Further, a solenoid coil can be formed on a microcircuit such as an integrated circuit or the like. And an integrated circuit having a small number of parts and having the stable characteristics of a circuit can be realized by connecting a single solenoid coil or plural coils having a required inductance performance. A high reliability with a small size can be expected from electronic appliances constructed of such an integrated circuit. And, the problem of delay that is expected from a larger-scale integrated circuit can be diminished by mounting solenoid coils in required positions.